Titanium alloy and method of manufacturing material for timepiece exterior part

Abstract

A titanium alloy of the present invention includes aluminum at a ratio of 28.0 at % or more and 38.0 at % or less, iron at a ratio of 2.0 at % or more and 6.0 at % or less, and titanium and inevitable impurities as the balance or includes aluminum at a ratio of 28.0 at % or more and 38.0 at % or less, manganese at a ratio of 4.0 at % or more and 8.0 at % or less, and titanium and inevitable impurities as the balance. Further, the titanium alloy of the present invention may include silicon at a ratio of 0.3 at % or more and 1.5 at % or less.

What is claimed is: 
     
       1. A method of manufacturing a material for a timepiece exterior part, the method comprising:
 a first heat treatment step of heating a casted titanium alloy at a temperature in a range of 1200° C. or higher and 1300° C. or lower in a furnace, the titanium alloy being cooled down at a room temperature thereafter by taking out from the furnace; 
 a forging step of forging the titanium alloy after the first heat treatment step at a room temperature in an atmosphere, or a hot working step of performing hot working on the titanium alloy after the first heat treatment step at a room temperature in an atmosphere; and 
 a second heat treatment step of heat-treating the titanium alloy at a temperature in a range of 1200° C. or higher and 1300° C. or lower after the forging step or the hot working step, the titanium alloy being cooled down to a room temperature thereafter to form a timepiece exterior part, 
 wherein the titanium alloy consists of: 
 aluminum at a ratio of 28.0 at % or more and 38.0 at % or less; 
 iron at a ratio of 2.0 at % or more and 6.0 at % or less; and 
 titanium and inevitable impurities as the balance, 
 wherein after the second heat treatment step, the titanium alloy is cooled at a cooling rate equal to or higher than that of air cooling, 
 the method is free of a surface hardening treatment step, and 
 the timepiece exterior part has a Vickers hardness of HV 600 or more. 
 
     
     
       2. A method of manufacturing a material for a timepiece exterior part, the method comprising:
 a first heat treatment step of heating a casted titanium alloy at a temperature in a range of 1200° C. or higher and 1300° C. or lower in a furnace, the titanium alloy being cooled down at a room temperature thereafter by taking out from the furnace; 
 a forging step of forging the titanium alloy after the first heat treatment step at a room temperature in an atmosphere, or a hot working step of performing hot working on the titanium alloy after the first heat treatment step at a room temperature in an atmosphere; and 
 a second heat treatment step of heat-treating the titanium alloy at a temperature in a range of 1200° C. or higher and 1300° C. or lower after the forging step or the hot working step, the titanium alloy being cooled down to a room temperature thereafter to form a timepiece exterior part, 
 wherein the titanium alloy consists of: 
 aluminum at a ratio of 28.0 at % or more and 38.0 at % or less; 
 iron at a ratio of 2.0 at % or more and 6.0 at % or less; 
 silicon at a ratio of 0.3 at % or more and 1.5 at % or less and 
 titanium and inevitable impurities as the balance, 
 wherein after the second heat treatment step, the titanium alloy is cooled at a cooling rate equal to or higher than that of air cooling, and 
 the method is free of a surface hardening treatment step, and 
 the timepiece exterior part has a Vickers hardness of HV 600 or more. 
 
     
     
       3. The method according to  claim 1 , wherein the titanium alloy consisting the timepiece exterior part is in a B2 phase of an intermetallic compound phase. 
     
     
       4. The method according to  claim 2 , wherein the titanium alloy consisting the timepiece exterior part is in a B2 phase of an intermetallic compound phase.